The invention relates to an injection mould having a cavity for receiving a plastics melt, the cavity comprising a plate-shaped first part and a plurality of hollow cylindrical second parts which are arranged next to one another perpendicularly to the first part, and having a temperature-control system which comprises both temperature-control channels divided into channel portions for transporting a temperature-control medium and a first and a second temperature-control medium connection.
Medical containers, in particular packaging for medical substances, are usually produced, packed and sterilised by primary packaging manufacturers under clean room conditions. Medical containers of this type can include syringe bodies, ampoules, pre-fillable syringes, cartridges, vials, bottles, cartridge needle units and glass cylinders. The medical containers can be produced from glass or plastics material. Typically however, the medical containers are not processed individually but are delivered in holding devices to the next production step, for example sterilisation or also siliconisation. The medical containers to be transported usually comprise a holding means, for example a flange which engages in the holding device so that the containers are held in a suspended manner. Holding devices of this type are also known as a “syringe nest”. Such holding devices are also used for further transportation to a bottler, for example. For this purpose, the holding device is introduced into a tank which is sealed with a membrane, thereby maintaining the sterility of the medical containers.
For example, a holding device of this type contains 100 or 160 receiving devices for a respective syringe, the diameter of a receiving device (also called a cylinder due to its shape) being for example 12.2 mm or 9.4 mm. The article to be produced “100 Nest Ø12.2 for RTF syringes” is accordingly characterised for example by a cylinder die or dome die respectively having a total of 100 cylinders (domes). These cylinders are joined together by connecting webs. The injection mould for producing a syringe nest of this type must accordingly have just as many cores to internally delimit the hollow cylindrical parts and a die to delimit the cavity.
According to a first instance, it would be conceivable that, during the production of a workpiece produced from a plastics material (for example from a thermoplastic), to solidify the melt, the amount of heat which is produced must be removed as efficiently as possible and thus it is necessary to use a temperature-control medium for cooling which has the lowest possible temperature, bearing in mind the required viscosity. According to a second instance, there are examples of plastics materials (for example thermosetting plastics and elastomers) which are still crosslinking in the mould and, for this they need to be heated, whereby the temperature-control medium should have a higher temperature for heating. The principles of the present invention would also operate for a heating procedure as the second instance analogously to the cooling procedure as the first instance; however, for the sake of simplicity, the present invention is only described for the first instance, i.e. for a cooling procedure.
Due to the relatively large component dimensions and to the described geometric conditions, during production by injection moulding, the described syringe nest exhibits a strongly pronounced distortion behaviour, which also leads to bending of the resulting moulding. Furthermore, due to the high volume of the moulding, the evolution of a relatively great amount of heat is to be expected during production which must be removed as efficiently as possible in view of the cooling time and thus also of the total cycle time.
In view of the shape of a workpiece to be produced, in this respect, a conformal cooling must be realised. Since the larger the available surface, the greater the transferable amount of heat, the amount of heat must be effectively removed particularly in the areas which are characterised by a low ratio of workpiece surface to workpiece volume. In the case of the syringe nest, these are in particular the areas in which the hollow cylindrical second parts come together and/or where they meet the first plate-shaped part.
To remove this quantity of heat, the moulds which are currently used are temperature-controlled by a serial cooling concept. This means that starting from a temperature-control medium connection, the temperature-control medium (usually water or oil) is transported successively through the cooling channel portions and thereby successively through the individual cores.
However, this cooling concept entails a very high loss of pressure in the cooling system, because all the individual pressure losses are added together. Due to this fact, the volume flow is throttled and the heat dissipation is greatly minimised. This adversely affects the cooling time and thereby adversely affects the total cycle time. This cooling concept cannot effectively counteract the strong distortion tendency of the article.
Furthermore, the only small volume flow can cause blockages in the cooling system because particles of dirt can be deposited relatively easily. This problem is known in practice and requires a great amount of maintenance.
In addition, this cooling concept suffers from the disadvantage of an irregular removal of heat at the article. The reason for this is that the cooling medium heats up between the coolant feed and coolant discharge. In the serial cooling concept, the temperature-control medium has a much lower temperature when it is transported through the first core compared to when it is transported through the last core. Consequently, the quantities of heat which are produced per core cannot be removed uniformly.
Furthermore, the high loss of pressure in the currently used serial cooling means that the pumping capacity of the temperature-control devices is not used efficiently. In this respect, the efficiency of the temperature-control device is reduced, which reduces the economic feasibility.
Thus, it is the object of the present invention to develop an injection mould having a cooling and temperature-control system or a temperature-control system respectively which is as simple and as efficient as possible and which provides a simple and clearly arranged cooling tubing and effectively uses the available cooling power of the temperature-control devices.